Features

Astronomik H-Alpha 6nm CCD Filter - 50mm Round Unmounted

The Astronomik 6 nm H-alpha filter is an extremely narrow emission-line filter for CCD photography. The filter lets the H-alpha light of emission nebulae pass and blocks nearly the whole remainder of the spectrum where the CCD is sensitive. The Full Width at Half-Maximum (FWHM) of 6 nm is optimized for a maximum contrast between the (H-alpha emitting) object and the background. The contrast gain is much higher than with our 12 nm emission line filters but you won't see as much stars in the resulting images. The design of the transmission curve makes it possible to use the filters with instruments from 1:3.75 to 1:15.

The Astronomik H-alpha-CCD (6 nm version) increases the contrast between objects, in this case between the H-alpha emission line and the skyglow background in the same way as the 12 nm version. The gain in contrast is much higher due to the smaller FWHM. The 6 nm H-alpha filter is the right choice for extremely dim objects, even in the Milky Way, and for observations from heavily light-polluted places. The Astronomik 6 nm H-alpha-CCD completely suppresses the emission lines of artificial lighting (mercury (Hg) and sodium (Na)) and skyglow. Transmission losses and chromatic distortions, which arise with other filters, only occur with Astronomik filters when extremely bright aperture ratios come into play.

Using the Astronomik 6 nm H-alpha together with the 12 nm H-alpha gives you the ability to have a maximum contrast in the HII objects and to keep the stars in the final image. The Astronomik 6 nm H-alpha filter may NOT be used for solar observation. If you plan to do (false-)color imaging with other emission line filters, you should get the matching filters with 12 nm FWHM. Images taken with filters with differing FWHM are very difficult to combine into the final image.